Pesticidal composition for water treatment

ABSTRACT

A pesticidal formulation for treatment of water to control water borne pests such as mosquitoes and blackfly or water hyacynth comprises tablets, granules or the like containing in their interior one or more pesticidal ingredients together with one or more effervescence-initiation components and a surface active dispersant so formulated that, when added to the water to be treated, they are capable of dispersing the pesticidal ingredients at or near the surface of the water.

This invention relates to pesticidal formulations for control ofwater-borne insect pests, in particular mosquitoes and blackfly andother water-borne pests e.g. invasive plants, in particular waterhyacinth.

The control of water borne pests such as mosquitoes and blackfly, wherethe larval and pupal forms live in water, is difficult for a number ofreasons. Firstly, the use of generally toxic pesticides iscontra-indicated in water containing other valued species. For thisreason, a biological pesticide derived from Bacillus thuringiensis,especially B.thuringiensis var. israelensis, is of great interest. Thebacteria contain a proteinaceous crystal toxin which is specificallytoxic to mosquito species (Culicidae) and blackfly species (Simulidae).In particular, the endotoxin produced by B. thuringiensis var.israelensis serotype H-14 is used for this purpose and is specific tothose species of insect which have (a) an alkaline gut (pH to 9) and (b)an enzyme complement suitable for degradation of the endotoxin crystal.In practice this means mosquitoes and blackfly only. Indeed, the B.thuringiensis pesticide is not harmful to organisms of the followingtypes: Amphibia; Crustacea; Molluscs; Ephemeroptera; Hemiptera; Odonata,fish, annelid worms, flatworms, Diptera, Coleoptera, Hymenoptera, andTrichoptera. Furthermore, the toxin is completely non-toxic to humansand mammals and thus is entirely safe for use in drinking watersupplies.

A second problem is that the larvae of mosquitoes and blackfly feed ator near the surface of the water. This means that the pesticide must besupplied in that region. It is of no use if the pesticidal compositionsinks to the bottom of the water or is diluted and dispersed throughoutthe water system.

In order to solve these problems, solid formulations of B. thuringiensistoxins have comprised either wettable powders and the like for sprayingonto water surfaces, or coated buoyant granules, in which the activematerial is adhering to the exterior of small particles which are of anappropriate density to remain at or near the water surface. Typically,the granules used are based on maize seeds (corn), porous clay orperlite granules and granules based on sand.

However, these granules have their own shortcomings. Floating granulesare prone to wind drift, causing them to be driven towards the edges ofopen water, rather than remaining dispersed evenly across the watersurface. Also, their relative lightness results in a tendency for themto lodge on foliage and thus not reach the water surface at all. On theother hand, coated sand granules tend to be too dense and do not spendlong enough at the water surface.

An alternative solid formulation consists of "briquettes" which areclaimed to have an activity for up to 30 days. In practice, these arefound to give irregular or patchy control.

Apart from solid formulations, as described above, liquid formulationsof B. thiringiensis have been proposed. For example, SU 369891-Sdescribes a stabilised suspension of B. thuringiensis comprising anaqueous culture containing added oxyethylated di- and tri- esters ofpentaerythritol with 6-12 carbon atom carboxylic acids. The non-ionicsurfactant helps to prevent the bacilli from sinking. U.S. Pat. No.4,166,112 describes a buoyant colloidal suspension of B. thuringiensisformed from a suspension of spores in dioxan containing an oil such asjojoba oil. However, the aqueous liquid formulations are heavy andrequire a whole cell culture rather than just the spores or the toxincrystals themselves, and solvents such as dioxan are undesirably toxicto aquatic species.

Apart from water-borne insect pests, other water-borne pests need to becontrolled by application of a suitable pesticide to the water surface.Another major class of water-borne pest, especially in tropical areas,is aquatic plants. Particularly troublesome are the floating plants suchas water hyacinth which clog waterways. Conventional spraying ofherbicides over water is difficult, especially in windy conditions whendrift is a problem. A solid formulation of a herbicide such as propanilwhich released the active material at the water surface would be verydesirable.

The formulation must thus be able to dispense the pestidicalingredient(s) at or near the water surface and so must, in the water,exhibit a suitable degree of buoyancy and dispersibility. At the sametime, it must not be prone to wind drift. We have now found that theserequirements can be met by formulating the pesticidal ingredient(s) in adisintegrating effervescent presentation: the effervescence providesbuoyancy, keeping the materials at or near the surface of the water, andalso aids dispersion of the contents.

According to the present invention, therefore, there is provided apesticidal formulation for water treatment comprising tablets, granulesor the like containing in their interior one or more pesticidalingredients together with one or more effervescence-initiatingcomponents and a surface active dispersant, and so formulated that, whenadded to the water to be treated, they are capable of dispersing thepesticidal ingredients at or near the surface of the water.

Dispersion occurs on the breakup of the tablet or granule and is ensuredby the inclusion of a survace active dispersant, e.g. an anionicsurfactant such as an alkylbenzene sulphonate, an alcohol sulfate, anether sulfate, a phosphate ester, a sulphosuccinate, an alkanesulphonate, an olefin sulphonate or petroleum sulphonate, a sarcosinateor a taurate. The dispersant of choice is sodium dioctylsulphosuccinate.

The effervescence-initiating components can comprise any conventionaleffervescent couple, for example a solid acid and a carbonate orbicarbonate, for example citric or malic acid together with sodiumbicarbonate. The pesticide, the effervescence-initiating components andthe surface active dispersant are formulated into suitable solid bodies,for example tablets of 0.1 to 5 g weight e.g. 0.2 to 1 g; and granulesof about 5 to 20 mg weight, e.g. 7.5 to 15 mg.

Buoyancy is considerably helped by the inclusion of low density buoyancyaids, for example, colloidal silica. Dispersion is improved by inclusionof a tablet disintegrant such as polyvinylpyrrolidone. In addition,tablets contain lubricants, binders and, if desired colouring agents, asrequired.

Granules can be formed by granulation of the pesticidal,effervesence-initiating and dispersant ingredients mentioned above in apaste formed from conventional granulating material, e.g. a filler suchas china clay and a non-aqueous fluid, for example a high molecularweight polyethylene glycol, such as PEG 4,000. Water free conditions areof course essential, in order to avoid activation of theeffervesence-initiators.

In a modification of the formulation according to this invention, smalltablets or granules can be loaded into an intermittent release cartridgeor the like so that over a period of days or weeks the waterprogressively comes in contact with batches of the tablets or granules.For example, a water-resistant cartridge with an open end can be chargedwith a number of tablets or granules. These can then be covered by awater soluble seal and another batch of tablets or granules loaded infollowed by another water-soluble seal etc so that the cartridgecomprises a sequence of compartments each containing tablets or granulesand separated from each other by a water soluble seal. The cartridgeshould be so constructed that it sinks to the bottom of the watersupply. After a short time, the water will dissolve away the first sealand the first batch of tablets or granules will be released and willrapidly rise to the surface as they effervesce and disintegrate. In duecourse the second seal will be dissolved and a fresh batch of tablets orgranules will be released and so on. In this way, reinfestation of thewater supply can be prevented without the need for additional visits totreat the water.

The pesticide of choice in the formulations according to the presentinvention will include a biological pesticide, i.e. a pesticide derivedfrom a natural parasite or infective agent, in particular a bacterialtoxin product which is selectively toxic to the insect species to beeradicated. Of particular importance is the toxin derived from Bacillusthuringiensis var. israelensis, in particular strain H-14. As thispesticide is highly selective, the compositions according to the presentinvention can be used to treat river and pond water where the fish orother animal life must be protected. Furthermore, since the material isnon-toxic to humans and mammals, it can be safely used to treat drinkingwater supplies.

However, it is possible that in other applications, for exampleirrigation ditches, unwanted stagnant water etc, where toxicity is notsuch a problem, other organic chemical insecticides of botanical orsynthetic origin, or herbicides, can be incorporated, for examplenatural or synthetic pyrethrins, phosphorus-based pesticides e.g.temephos, and herbicides such as propanil. For choice, however, theformulations according to the present invention will contain B.thuringiensis-based products in view of their well- recognised activityand safety.

Field trials of granules containing a B. thuringiensis var israelensisH-14 preparation were carried out as follows.

The experimental site was a drainage ditch which ran from the south tothe sea in the north. The water within the ditch was stagnant exceptafter heavy rain when it began to flow into the sea.

METHODS

The ditch was divided into five sections with wooden planks. Eachsection was made water-tight by packing mud around each of the planks.The surface area of the water in each of the sections was obtained bymeasuring the width of the ditch at water level at intervals of 1m,calculating the mean width and multiplying by the length of the section.Water samples were taken for subsequent analysis of pH, turbidity, andsalinity. The air temperature and water temperature 5 cm beneath thesurface were measured with a thermometer. The extent of surfacevegetation, `scum` etc. was estimated. A sample of larvae were taken andpreserved in alcohol for identification. Ten dips were taken with aladle (350 ml capacity with a 13 cm diameter rim) at approximately 0.5 mintervals in each section of the ditch. The number of each instar andwhether they were alive or dead were recorded.

The northern-most section of ditch (nearest the sea) was labelledSection A, and so on to Section E, the most southerly (inland) section.Each section was treated as below:

Section A: treated with 30% less than recommended dose granules

Section B: treated with standard recommended dose granules (see below)

Section C: treated with 30% more than recommended dose granules

Section D: untreated Control

Section E: untreated, to be used as a larvae stock for bioassays.

The relevant quantities of granules were determined for each sectionaccording to the water surface area and the required treatment. Thegranules were applied evenly over the water surface in each of the threetreated sections. After time intervals of 30 minutes, 1 hour, 2 hours,24 hours, 48 hours and 96 hours after treatment, five 80 ml samples ofwater were taken at 0.5m intervals from sections A, B, C and D using asmall ladle (40 ml capacity with a 6 cm diameter rim). Each sample wasplaced in a plastic bioassay (250 ml capacity, 8.5 cm diameter and 6 cmdeep). The samples were sheltered from wind, rain and direct sunlight atoutdoor temperature. Into each sample were placed 10 larvae (1st, 2ndand 3rd instars) obtained from the untreated section E. These sampleswere inspected at 24 hours, 48 hours and 96 hours and the number of deadlarvae per sample counted.

As well as conducting bioassays, at 24 hours, 48 hours and 96 hours tendips were taken from each of the sections, A, B, C and D as describedabove. The number of each instar and whether they were dead or alive wasnoted.

RESULTS

The surface of each of the sections of the ditch were covered with athick mass of green algae. It was estimated that this algae covered 40%of the surface area of section A, 50% of section B, 50% of section C and60% of section D. The bed of the ditch was composed of black smelly mud,an indication of high organic content. Crustacea such as Cyclops wereabundant in each section indicated at high bacterial presence. The pH ofthe water was found to be 8.2. Turbidity was measured using aspectrometer at a wavelength of 315 nm and the sample was found to havean average absorbance value of 0.269, and an average light transmissionvalue of 52.5% relative to distilled water. Salinity measured by thehydrometric method was found to be 5.9 parts/1000. The temperaturevaried greatly throughout the trial.

As the water surface of each of the sections was densely covered withgren algae, and fourth instar larvae were present, it was decided to usethe higher recommended dose of 2 g granules per 10 m². The granulescontained 600 ITU/mg (ITU reference standard 1PS--78 (WHO)--see Bulletinof the ESA, Spring 1984 pp 26-29). The surface areas of the sections andthe quantities of the granules used were calculated as:

    ______________________________________                                        Surface       Recommend- Dose                                                 Area          ed dose    Applied                                              ______________________________________                                        Section A                                                                             2.21 m.sup.2                                                                            0.442 g    0.31 g (30% less than                                                         recommended)                                     Section B                                                                             1.86 m.sup.2                                                                            0.372 g    0.37 g (recommended                                                           dose)                                            Section C                                                                             1.72 m.sup.2                                                                            0.344 g    0.45 g (30% more than                                                         recommended dose)                                Section D                                                                             2.24 m.sup.2                                                                            0.448 g    0.00 g (control)                                 ______________________________________                                    

RESULTS FROM DIPPING ASSAYS

It is clear from the following table that the proportion of dead larvaeper dip increased after treatment in the treated sites, the control siteremaining relatively free of dead larvae. The overall number of larvaeper dip also decreased, which at first sight could be interpreted asbeing the result of the treatment. However, the means number of larvaeper dip in the control pond also decreased. This was largely due to thedrying up of the control pond and the larvae being caught in the mud orsheltering under the algae to prevent overheating and desiccation. Thewater level in sections A and B did not change to any noticable extent,however the level and surface areas of section C and D did changesignificantly. The drying up of these sections made sampling difficultand will have affected the number and distribution of larvae, so someinaccuracy will be found in the calculations of the effectiveness of thetreatments.

    ______________________________________                                        Live larvae present in the treated section relative to                        the control pond (%)                                                                     Section A                                                                              Section B Section C                                       ______________________________________                                        Prior to                                                                              Actual   44.8       59.8    60.3                                      Treatment                                                                             Corrected                                                                              100.0      100.0   100.0                                     24 h after                                                                            Actual   22.9       15.5    28.7                                      Treatment                                                                             Corrected                                                                              51.1       38.5    47.6                                      48 h after                                                                            Actual   18.8       14.6    10.4                                      Treatment                                                                             Corrected                                                                              41.2       24.4    17.3                                      96 h after                                                                            Actual   28.6       19.0    14.3                                      Treatment                                                                             Corrected                                                                              63.7       31.9    23.7                                      ______________________________________                                    

The following formula (an extended Abbot's formula) was used tocalculate the effectiveness of the treatments in terms of life larvaepresent in the treated ponds relative to the control pond at the time ofsampling after treatment as a percentage: ##EQU1## Where N_(t) is thenumber of live larvae per dip in the treated site after treatment

N_(c) is the number of larvae per dip in the control site after treatmenof other sites has begun

N_(to) is the number of larvae per dip in the treated site beforetreatment

N_(co) is the number of larvae per dip in the control site beforetreatment of the other sites has begun

By 48 hours the treatment had reduced the number of larvae to 42.1% insection A, 24.4% in section B, and 17.3% in section C (corrected values)relative to control site.

RESULTS FROM BIOASSAYS

Abbot's formula was used to determine the corrected mortality in eachset bioassays: ##EQU2##

The mortality in each of the replicate bowls within each treatmentdiffered considerably in the samples taken on the day of application,possibly due to uneven dispersion of the product as a consequence of thedense algae covering much of the water surface.

It was evident that the water samples from the treated sites wereeffective agains the larvae with high mortalities after only 24 hoursimmersion. Practically complete mortality occurred after 96 hoursimmersion.

CONCLUSIONS

Both sets of data, from the dipping and bioassays clearly showed thatthe new formulation in highly effective against the British mosquitoAedes detritus even in sites with fairly high organic pollution anddense surface vegetation. The data from the dipping assays appeared toshow a correlation between dosage and mosquito mortality. This was notapparent in the bioassay data. The bioassays sow that the potency of theformulation is greatly reduced 24 hours after application, and isnon-existant after 48%. This is probably due to the small particle sizeof the Bti resulting in it sinking very rapidly, and alsobiodegradation.

The following Examples will illustrate the invention:

EXAMPLE 1 Effervescent Tablets (50% active ingredient) Activeingredient: Bacillus thuringiensis var israelensis serotype H14.Ingredients

    ______________________________________                                                                  % w/w                                               ______________________________________                                        Active ingredient                                                                              2,000 ITU/mg primary powder                                                                      *50.0%                                    Surface active                                                                dispersant       sodium dioctylsulphosuccinate                                                                    15.0%                                     Tablet           polyvinylpyrrolidone                                                                             4.0                                       disintegrant                                                                  Buoyancy aid     silica             5.0%                                      Lubricant        magnesium stearate 1.0%                                      Binder           microcrystalline cellulose                                                                       9.0%                                       Effervescence    citric acid (anhydrous)                                                                          4.0%                                     Initiators       sodium bicarbonate to 100%                                   ______________________________________                                         *To give a potency of 1,000 ITU/mg of tablet.                            

The tablet ingredients are mixed and compressed sufficiently to avoidcrumbling during handling or in transit, but not so much as to cause thetablets to sink when applied to water. It has been found frommeasurements in the laboratory that a 5 g tablet with the followingdimensions meets the required standards:

    ______________________________________                                        Weight:            5 g +/- 0.25 g                                             Length:            40 mm                                                      Width:             13.5 mm                                                    Thickness:         12 +/- 0.60 mm                                             ______________________________________                                    

Moisture content

The lowest possible moisture content is desirable to avoid deteriorationof the tablets on storage. Moisture content is normally 2.5-3.5% asmeasured by the Dean & Stark method.

Effervescence

The tablets should float within 5 seconds of being applied to water at20° C. and should start to effervesce immediately on the water surface.

EXAMPLE 2 100 mg Mini-tablets (15% active ingredient) Ingredients

    ______________________________________                                                                  % w/w                                               ______________________________________                                        Active ingredient                                                                              4,000 ITU/mg primary powder                                                                      *15.0%                                    Surface active                                                                dispersant       sodium dioctylsulphosuccinate                                                                    15.0%                                     Tablet           polyvinylpyrrolidone                                                                             4.0%                                      disintegrant                                                                  Buoyancy aid     silica             5.0%                                      Lubricant        magnesium stearate 1.0%                                      Binder           microcrystalline cellulose                                                                       9.0%                                       Effervescence    citric acid (anhydrous)                                                                          12.0%                                    Initiators       sodium bicarbonate to 100%                                   ______________________________________                                         *To give a potency of 600 ITU/mg of tablet.                              

The tablets are compressed as in Example 1.

EXAMPLE 3 Water dispersible granules (5% & 15% active ingredient)Ingredients

    __________________________________________________________________________                             5.0%   15.0%                                         __________________________________________________________________________    Active                                                                        ingredient                                                                              4,000 ITU/mg primary powder                                                                  5.0%** 15.0%*                                        Surface active                                                                dispersant                                                                              sodium dioctylsulphosuccinate                                                                15.0%  15.0%                                         Binder    microcrystalline cellulose                                                                   5.0%   5.0%                                          Filler    china clay     2.0%   2.0%                                          Granulating                                                                   liquid    PEG 4000 (molten)                                                                            approx 13.0%                                                                         13.0%                                          Effervescence                                                                           Citric acid (anhydrous)                                                                      15.0%  12.5%                                        Initiators                                                                              Sodium bicarbonate                                                                           to 100%                                                                              to 100%                                       __________________________________________________________________________     **To give a potency of 200 ITU/mg                                             *To give a potency of 600 ITU/mg                                         

Moisture content

The lowest possible moisture content is desirable to avoid deteriorationof the granules on storage. Moisture content is normally 2.5-3.5% asmeasured by the Dean & Stark method.

Effervescence

The granules should float within 5 seconds of being applied to water at20° C. and should start to effervesce immediately on the water surface.

Granule size

The granules are nominally 2 mm in diameter and up to approximately 5 mmin length, not more than 1% "fines" should pass a 1 mm sieve.

Density

Bulk density is normally 0.55+/-0.05 g/cc Packing density is normally060+/-0.05 g/cc.

EXAMPLE 4

    ______________________________________                                        5% Temephos Tablets                                                           ______________________________________                                        temephos technical   5.0                                                      sodium dioctylsulphosuccinate                                                                      15.0%                                                    polyvinylpyrrolidnne 5.0%                                                     silica               8.0%                                                     magnesium stearate   1.0%                                                     microcrystalline cellulose                                                                         10.0%                                                    citric acid (anhydrous)                                                                            14.0%                                                    sodium bicarbonate   to 100%                                                  ______________________________________                                    

EXAMPLE 5

    ______________________________________                                        0.5% Pyrethrins Tablets                                                       ______________________________________                                        2.5% pyrethrins dust concentrate                                                                   2.0%                                                     sodium dioctylsulphosuccinate                                                                      15.0%                                                    polyvinylpyrrolidone 4.0%                                                     silica               5.0%                                                     magnesium stearate   1.0%                                                     microcrystalline cellulose                                                                         9.0%                                                     citric acid (anhydrous)                                                                            16.0%                                                    sodium bicarbonate   to 100%                                                  ______________________________________                                    

EXAMPLE 6

    ______________________________________                                        5% Temephos Granules                                                          ______________________________________                                        temephos technical   5.0                                                      sodium dioctylsulphosuccinate                                                                      15.0%                                                    microcrystalline cellulose                                                                         5.0%                                                     china clay           2.0%                                                     PEG 4000 (molten)    13.0                                                     citric acid (anhydrous)                                                                            15.0%                                                    sodium bicarbonate   to 100%                                                  ______________________________________                                    

EXAMPLE 7

    ______________________________________                                        0.5% Pyrethrins Granules                                                      ______________________________________                                        2.5 pyrethrins dust concentrate                                                                    2.0%                                                     sodium dioctylsulphosuccinate                                                                      15.0%                                                    microcrystalline cellulose                                                                         5.0%                                                     china clay           2.0%                                                     PEG 4000 (molten)    13.0                                                     citric acid (anhydrous)                                                                            15.0%                                                    sodium bicarbonate   to 100%                                                  ______________________________________                                    

EXAMPLE 8

    ______________________________________                                        35% Propanil Tablets                                                          ______________________________________                                        35% propanil technical                                                                             35.0%                                                    sodium dioctylsulphosuccinate                                                                      15.0%                                                    polyvinylpyrrolidone 4.0%                                                     silica               5.0%                                                     magnesium stearate   1.0%                                                     microcrystalline cellulose                                                                         9.0%                                                     citric acid (anhydrous)                                                                            7.5%                                                     sodium bicarbonate   to 100%                                                  ______________________________________                                    

EXAMPLE 9

    ______________________________________                                        35% Propanil Granules                                                         ______________________________________                                        35% Propanil technical                                                                             35.0%                                                    sodium dioctylsulphosuccinate                                                                      15.0%                                                    microcrystalline cellulose                                                                         5.0%                                                     china clay           2.0%                                                     PEG 4000             13.0%                                                    citric acid (anhydrous)                                                                            7.5%                                                     sodium bicarbonate   to 100%                                                  ______________________________________                                    

EXAMPLE 10 Controlled-Release Tubes & Cartridges

Controlled-release tubes are solid biodegradable cardboard tubes packedwith 3-4 small quantities of granules each separated by a thin layer ofwater soluble wax. The granules used are the 15% effervescent granulesas described in the Example 3. The method of application is simply totoss one of the tubes into a mosquito infested pond. After a short timethe water soluble wax plug in the top of the tube dissolves allowing thefirst batch of granules to come in contact with the water. The granulesrise to the water surface, effervesce and disperse the Bt (or otherinsecticide) across the surface. Gradually over the next week to 10 daysthe second layer of water soluble wax dissolves allowing release of thesecond dose of insecticide and so on. The typical persistence of Bt inthe environment is 2-3 days.

The water soluble wax normally used in polyethylene glycol (PEG)molecular weight 4000. Other molecular weight PEGs have been used and asa general rule the higher molecular weight waxes dissolve more slowlygiving a longer interval between doses. Other factors affecting rate ortime of release are water temperature (higher temperature leads toquicker release) and was thickness (thinner wax leads to quickerrelease). With these parameters in mind, a suitable formulation can beprovided for any particular application.

We claim:
 1. A pesticidal formulation in tablet, granule, or pellet formfor water treatment comprising:a. an effective amount of at least onebiological pesticidal ingredient; b. at least oneeffervescent-initiating component; c. at least one surface activedispersant; d. a lubricant; e. a binder; f. a disintegrant; and g. a lowdensity buoyancy aidwherein said biological pesticidal ingredient is aBacillus thuringiensis var. israelensis preparation and wherein saidpesticidal formulation is formulated so as to disperse said pesticidalingredient at or near the surface of the water to be treated.
 2. Theformulation according to claim 1 wherein said surface active dispersantis an anionic surfactant selected from the group consisting of analkylbenzene sulphonate, an alcohol sulfate, an ether sulfate, aphosphate ester, a sulphosuccinate, an alane sulphonate, an olefinsulphonate, a petroleum sulphonate, a sarcosinate and a taurate.
 3. Acontrolled-release formulation for water treatment comprising:1. apesticidal formulation comprising:a. an effective amount of at least onebiological pesticidal ingredient; b. at least oneeffervescent-initiating component; c. at least one surface activedispersant; d. a lubricant; e. a binder; f. a disintegrant; g. a lowdensity buoyancy aid, and
 2. at least one water-soluble polymer whereinsaid biological pesticidal ingredient is a Bacillus thuringiensis var.israelensis preparation.
 4. a pesticidal formulation according to claims1 or 3 wherein said disintegrant comprises polyvinylpyrrolidone.
 5. Apesticidal formulation according to claims 1 or 3 wherein said lowdensity buoyancy aid comprises colloidal silica.
 6. The formulationaccording to claim 3 wherein said surface active dispersant is ananionic surfactant selected from the group consisting of an alkylbenzenesulphonate, an alcohol sulfate, an ether sulfate, a phosphate ester, asulphosuccinate, an alkane sulphonate, an olefin sulphonate, a petroleumsulphonate, a sarcosinate and a taurate.
 7. A pesticidal formulationaccording to claim 2 or claim 6 wherein said surface active dispersantcomprises sodium dioctylsulphosuccinate.
 8. The formulation accordign toclaim 3 wherein said water-soluble polymer comprises a polyethyleneglycol polymer.
 9. A method of controlling water-borne pests comprisingdosing water with a pesticidal formulation comprising:a: an effectiveamount of at least one biological pesticidal ingredient; b. at least oneeffervescent-initiating component; c. at least one surface activedispersant; d. a lubricant; e. a binder; f. a disintegrant; and g. a lowdensity buoyancy aidwherein said biological pesticidal ingredient is aBacillus thuringiensis var. israelensis preparation and wherein saidpersticidal formulation is formulated so as to disperse said pesticidalingredient at or near the surface of the water to be treated.
 10. Amethod of controlling water-borne pests comprising dosing water with acontrolled-release formulation according to claim
 3. 11. A method ofcontrolling water-borne pests by dosing infested water with a pesticidalformulation according to claim 1.